Linked zones: shared records kept in step across views

Zones of the same name in different views can be linked. Shared records
are kept in step: a change in one view reaches the others in the same
changeset, as explicit operations, so the diff, permission checks,
history and undo cover every view. Records local to a view override the
shared records of that name and type there; removing the override brings
the shared ones back, and sharing a view's version makes it every view's.
Each zone keeps its own options, serial and file.

Linking existing zones changes no answer: what is the same everywhere
becomes shared, the rest stays local. Unlinking keeps every record, all
local. ACME challenges are written once per link, and --view all changes
a link once. jarl zone link/unlink, zone create --link-with, record
--local/--shared, LINK column, web UI controls, POST /zones/{zone}/link
and /unlink, validation checks linked_*, store migration 11, docs and
e2e.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

internal/model/linked.go

@@ -0,0 +1,101 @@
+package model
+
+import (
+	"slices"
+	"sort"
+)
+
+// Linked zones (docs/views.md#linked-zones): zones of the same name in
+// different views whose shared records Jarl keeps in step. Each zone
+// keeps its own copy of every shared record (with the same SharedID), so
+// named, validation and rendering see ordinary zones. A record with
+// SharedID 0 in a linked zone is local to its view: an override of the
+// shared records of the same name and type there.
+
+// LinkMembers returns the zones of a link group in view order.
+func (s *State) LinkMembers(group int64) []*Zone {
+	if group == 0 {
+		return nil
+	}
+	var out []*Zone
+	for _, z := range s.Zones {
+		if z.LinkGroup == group {
+			out = append(out, z)
+		}
+	}
+	s.SortByView(out)
+	return out
+}
+
+// LinkedWith returns the other zones z is linked with, in view order.
+func (s *State) LinkedWith(z *Zone) []*Zone {
+	var out []*Zone
+	for _, o := range s.LinkMembers(z.LinkGroup) {
+		if o.ID != z.ID {
+			out = append(out, o)
+		}
+	}
+	return out
+}
+
+// AnyLinked reports whether any zone is linked.
+func (s *State) AnyLinked() bool {
+	for _, z := range s.Zones {
+		if z.LinkGroup != 0 {
+			return true
+		}
+	}
+	return false
+}
+
+// SortByView sorts zones in view order.
+func (s *State) SortByView(zs []*Zone) {
+	pos := func(z *Zone) int {
+		if v := s.Views[z.ViewID]; v != nil {
+			return v.Position
+		}
+		return -1
+	}
+	sort.Slice(zs, func(i, j int) bool {
+		if a, b := pos(zs[i]), pos(zs[j]); a != b {
+			return a < b
+		}
+		return zs[i].ID < zs[j].ID
+	})
+}
+
+// RRset returns the records of one name and type in a zone, by ID.
+func (s *State) RRset(zoneID int64, name, typ string) []*Record {
+	var out []*Record
+	for _, r := range s.Records {
+		if r.ZoneID == zoneID && r.Name == name && r.Type == typ {
+			out = append(out, r)
+		}
+	}
+	slices.SortFunc(out, func(a, b *Record) int { return int(a.ID - b.ID) })
+	return out
+}
+
+// HasLocal reports whether a linked zone overrides the shared records of
+// one name and type with records of its own.
+func (s *State) HasLocal(zoneID int64, name, typ string) bool {
+	for _, r := range s.Records {
+		if r.ZoneID == zoneID && r.Name == name && r.Type == typ && r.SharedID == 0 {
+			return true
+		}
+	}
+	return false
+}
+
+// SharedRecords returns a zone's shared records of one name and type,
+// by SharedID.
+func (s *State) SharedRecords(zoneID int64, name, typ string) []*Record {
+	var out []*Record
+	for _, r := range s.Records {
+		if r.ZoneID == zoneID && r.Name == name && r.Type == typ && r.SharedID != 0 {
+			out = append(out, r)
+		}
+	}
+	slices.SortFunc(out, func(a, b *Record) int { return int(a.SharedID - b.SharedID) })
+	return out
+}

internal/model/model.go

@@ -166,6 +166,10 @@ type Zone struct {
 	// Disabled zones stay in Jarl, records and all, but named doesn't
 	// load them: their zone statement is left out of named.conf.
 	Disabled bool `json:"disabled,omitempty"`
+	// LinkGroup links zones of the same name in different views: Jarl
+	// keeps their shared records in step (docs/views.md#linked-zones). 0
+	// for a zone that isn't linked; linked zones share the ID.
+	LinkGroup int64 `json:"link_group,omitempty"`
 	Meta
 }
 
@@ -195,6 +199,10 @@ type Record struct {
 	// Disabled records stay in Jarl but are left out of the zone (the
 	// zone file lists them as comments).
 	Disabled bool `json:"disabled,omitempty"`
+	// SharedID ties the copies of a shared record in linked zones
+	// together (the same in every copy). 0 for a record of a zone that
+	// isn't linked, and for a record local to its view in one that is.
+	SharedID int64 `json:"shared_id,omitempty"`
 	Meta
 }